Methylene Chloride Thermo Fisher

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Thermo Fisher Scientific supplies methylene chloride (dichloromethane, CAS 75-09-2, CH₂Cl₂) under multiple analytical designations, including HPLC grade, Certified ACS reagent grade, and Optima high-purity variants. The molecule has a molar mass of 84.93 g/mol and is shipped in 1 L, 2.5 L, 4 L, 20 L, and 200 L containers with inert headspaces appropriate to the grade. The product line is used in normal-phase high-performance liquid chromatography, trace-level extraction, cleaning validation, organic synthesis, and environmental semivolatile sample preparation. The primary difference relative to technical dichloromethane is not thermodynamic selectivity but the control of UV absorbance, water, acidity, nonvolatile residue, and trace metals. Product-specific certificates of analysis are issued for every lot, and the acceptance windows vary by grade; the exact numerical criteria must be read from the lot-specific document rather than assumed from published technical summaries.

What Impurity Specifications Differentiate HPLC-Grade Dichloromethane from Technical Grade?

HPLC-grade methylene chloride from Thermo Fisher is controlled for absorbance that permits ultraviolet detection above the solvent cutoff near 233 nm. Gas chromatographic assay using flame ionisation detection is reported on each certificate of analysis; typical acceptance is not less than 99.8% for the HPLC designation, although the exact result is lot-specific and should be obtained from the current certificate. Water content is measured by coulometric Karl Fischer titration, and nonvolatile residue is determined by evaporation of a defined volume and gravimetric weighing. The technical grade used in closed-loop vapour degreasing is not controlled for these same constraints; it can contain higher unsaturates, chlorinated by-products, stabilizer breakdown products, and nonvolatile residue. In trace-level separations, those impurities can co-elute or suppress ionisation under electrospray conditions. For a normal-phase HPLC method using a 4.6 mm × 250 mm, 5 µm silica column operated at 1.0 mL/min with 254 nm ultraviolet detection, mobile-phase impurity excursions produce baseline drift and quantitation uncertainty. The HPLC designation is selected for such work because the certificate of analysis provides lot-specific UV absorbance at specified wavelengths, water content, and residue after evaporation. Published data for this specific configuration is limited, but the documented acceptance windows distinguish analytical solvent from technical stock.

When Stabilizer Addition Alters Detector Response or Reactor Compatibility

Stabilized methylene chloride commonly contains amylene or cyclohexane at trace concentrations to inhibit oxidative decomposition and acid formation during storage. The Thermo Fisher product line includes amylene-stabilized and nonstabilised selections because stabilizer compatibility differs across downstream methods. In electron-capture detection, unsaturated or halogenated stabilizers can produce baseline excursions; the nonstabilised grade is specified when detector cleanliness is critical. In synthesis, an amylene-stabilised grade may introduce a small alkene impurity that participates in sensitive organometallic reactions. The Certified ACS grade is chosen where reagent-defined limits on stabilizer and acidity are mandated by an internal method transfer or collaboration protocol. The stabilizer content is not an inert diluent; it must be assessed when the solvent is used for phase-transfer catalysis or when the solvent is later removed by rotary evaporation at 40 °C under reduced pressure, where amylene may be partially retained in concentrated extracts. Analytical-grade dichloromethane from other suppliers can use ethanol or cyclohexane as stabilizer, and retention-time behaviour of these stabilizers can interfere with early-eluting extractables when analytes have log P values below 2. The absence of a stabilizer in the nonstabilised grade reduces that interference but increases sensitivity to oxygen and light; the product should be stored under inert gas after opening when that designation is used.

Residual active pharmaceutical ingredient extraction from 316L stainless steel coupons with a 0.8 µm Ra surface finish is performed by immersion or sonication in methylene chloride for cleaning validation. The high density relative to water allows the immiscible lower dichloromethane phase to contact the coupon surface without floating surface residues. In US EPA SW-846 Method 3510C, separatory funnel liquid-liquid extraction of semivolatile organics from aqueous matrices uses dichloromethane as the extraction solvent. Because the solvent has a density of 1.325 g/mL at 25 °C, the organic phase is collected from the bottom stopcock; three successive 60 mL portions per 1 L of water are typical. Emulsion formation is controlled with continuous-phase mixing and, when necessary, mechanical phase separation using a centrifuge at 2,000 × g for 10 min. The use of analytical rather than technical dichloromethane reduces the frequency of solvent-blank correction in gas chromatography–mass spectrometry extractable methods, but blank runs remain necessary because the solvent is not free of all background ions. In high-shear dispersions of poorly soluble actives, the same solvent can be used as a wetting agent, but the low viscosity and high vapour pressure require closed mixing vessels to avoid evaporative cooling and water condensation.

In a 50 L glass-lined extractor with bottom discharge and a PTFE stopcock, the heavier dichloromethane phase is transferred by nitrogen pressure at 0.5 bar to avoid pump cavitation caused by vapour locking. Batch-to-batch differences in technical solvent can accumulate in the reboiler and foul heat-transfer surfaces during solvent recovery; the lower residue specifications of the analytical product reduce that fouling at the expense of higher unit cost. For routine quality-control extraction of thermally labile analytes, the extractor is operated at 15 °C to 20 °C jacket temperature to limit thermal decomposition; a −20 °C condenser on the recovery line returns solvent to the extractor without atmospheric moisture ingress. Published data for this specific configuration is limited, but the performance of glass-lined equipment with this solvent is well documented in pharmaceutical intermediate manufacturing. The heavier phase is sampled from the bottom, and the sample line should be stainless steel or PTFE; polycarbonate sight glasses are incompatible with prolonged contact. This equipment boundary exists because dichloromethane can stress-crack polycarbonate and acrylic, and gasket selection must be limited to PTFE envelope gaskets or chemical resistant elastomers with documented permeation data.

Physical property, packaging, and handling limits constrain solvent-transfer productivity

Methylene chloride has a density of 1.325 g/mL at 25 °C, a refractive index of 1.4242 at 20 °C, and a boiling range of 39.8 °C to 40.0 °C. The vapour pressure is approximately 47 kPa at 20 °C, so open transfers at room temperature generate concentrations that can exceed the OSHA permissible exposure limit of 25 ppm as an 8-hour time-weighted average and the short-term exposure limit of 125 ppm. The product is classified as UN 1593, Class 6.1, Packing Group III. Amber glass bottles with PTFE-lined closures reduce photolytic degradation and maintain low water ingress; metal containers are used for larger volumes but must be constructed from carbon steel or stainless steel with no aluminium internals because dichloromethane can react with aluminium under certain conditions. Transfer lines should be PTFE, stainless steel, or polypropylene; flexible vinyl tubing is unsuitable because plasticizer migration can occur. The table below lists physical properties that are routinely confirmed by supplier certificates of analysis.

Because methylene chloride is aggressive toward polycarbonate, acrylic, and many elastomer seals, pump heads in HPLC systems must be equipped with PTFE or stainless steel wetted parts when the solvent is used as a mobile-phase modifier. A 100 mL/min nitrogen purge across the reservoir is used in moisture-sensitive normal-phase methods to reduce water absorption during long sequence runs. Solvent pre-filtration through a 0.2 µm PTFE membrane removes particulate after transfer from the original container; recirculation through the pump is not recommended because of potential stabilizer redistribution at elevated temperature. In normal-phase applications, water content above 0.02% can shift retention times for polar analytes. The exact water tolerance should be established by standard addition, using reagent water added at 50 ppm increments, and monitored by gas chromatography–mass spectrometry of the eluent. The product’s low UV cutoff does not make it a universal mobile phase for sub-230 nm detection, where hexane or heptane systems are more transparent. For that reason, dichloromethane is used primarily at 254 nm or with refractive index or evaporative light-scattering detection.

Relative to chloroform and carbon tetrachloride, dichloromethane has a lower tendency to form free radicals in the presence of peroxides, but it cannot be regarded as a nonreactive diluent in all sample matrices. In normal-phase LC method transfer between Thermo Fisher methylene chloride and a competitor’s analytical solvent, the retention-time order is preserved because the solvent strength and polarity are intrinsic properties; the observable differences appear in the solvent blank, coulometric water uptake after opening, and evaporative residue after standard concentration. Chromatographers who replace a military-specification cleansing solvent with the HPLC designation must verify that the extraction method’s detection limit is not limited by the solvent blank. That verification is typically executed by concentrating 250 mL of the incoming solvent to 1.0 mL and injecting 1 µL into a gas chromatograph with a 30 m × 0.25 mm, 0.25 µm film column; absence of non-target peaks above the baseline noise threshold is the acceptance criterion. The same blank-concentration protocol is used in environmental methods where extractables from bottle closures can be mistaken for analytes. Because the Thermo Fisher product is provided in solvent-rinsed glass with PTFE-lined caps, the closure-related blank is reduced but not eliminated; solvent quality must be re-verified after the bottle has been opened more than once.

The product differs from industrial dichloromethane not by chemical identity but by the analytical controls that prevent impurity carryover into regulated workflows. Under ICH Q3C, methylene chloride is a Class 2 solvent with a permitted daily exposure of 6.0 mg/day and a concentration limit of 600 ppm in pharmaceutical products; this does not preclude its use as a manufacturing or extraction solvent provided that the residual solvent is controlled and validated. Under European Union REACH Regulation Annex XVII Entry 59, paint-stripper formulations containing methylene chloride at or above 0.1% by weight are restricted; this regulatory boundary means that high-purity laboratory solvent is not a drop-in replacement for industrial painter stripper stock. In the United States, the OSHA permissible exposure limit is 25 ppm over an 8-hour TWA with a short-term exposure limit of 125 ppm; local exhaust ventilation and solvent-resistant laminate barrier gloves with documented permeation breakthrough times are required. The requirement for lot-specific trace metal reporting by inductively coupled plasma mass spectrometry separates the Optima product from generic HPLC solvents; published data for this specific configuration is limited, but analytical chemists rely on the certificate of analysis to define the residual elements measured at or below 1 µg/L for high-sensitivity applications. In contrast, the Certified ACS grade is aligned with the ACS Committee on Analytical Reagents monographs, which define acceptance methods for assay, water, residue after evaporation, acidity, and stabilizer concentration. That alignment with a published compendial approach is an important difference when methods must be defended during regulatory inspection.

For analysts comparing the Thermo Fisher methylene chloride line with industrial or technical dichloromethane, the material difference resides in controlled UV absorbance, residue and water limits, stabilizer documentation, and packaging inertness. The solvent remains chemically identical in thermodynamic selectivity to technical dichloromethane, so swapping to the analytical product does not alter partition coefficients in liquid-liquid extraction. It does reduce the frequency of blank detections caused by stabilizer oxidation products and column contamination in normal-phase separations. However, operational incompatibilities remain: the solvent should not be combined with strong bases, reactive metals, or open flames, and it must be stored in containers designed to withstand vapour pressure at ambient temperature. The product’s reduced stabilizer content can also require stricter headspace control after opening; if the bottle is left under ambient air for extended periods, the certificate of analysis no longer represents the current water and oxidative degradation profile. For trace-level extraction, a solvent blank should be run through the entire method, including rotary evaporation at 40 °C and reconstitution to 1.0 mL, to confirm that nonvolatile residue remains below the method reporting limit. A blank value above the reporting limit indicates container contamination, transfer-line plasticizer migration, or stabilizer retention and must be resolved before sample data are accepted.